diff --git a/src/exabgp/bgp/message/open/capability/capabilities.py b/src/exabgp/bgp/message/open/capability/capabilities.py
index 013fa3789..70d00ec64 100644
--- a/src/exabgp/bgp/message/open/capability/capabilities.py
+++ b/src/exabgp/bgp/message/open/capability/capabilities.py
@@ -26,7 +26,7 @@
 
 from exabgp.bgp.message.notification import Notify
 
-from struct import pack
+from struct import pack, unpack
 
 # =================================================================== Parameter
 #
@@ -201,6 +201,21 @@ def pack(self):
 
     @staticmethod
     def unpack(data):
+        def _extended_type_length(name, data):
+            if len(data) < 3:
+                raise Notify(2, 0, "Bad length for OPEN (extended) %s (<3) %s" % (name, Capability.hex(data)))
+            # Optional parameters length
+            ld = unpack('!H', data[1:3])[0]
+            boundary = ld + 3
+            if len(data) < boundary:
+                raise Notify(
+                    2, 0, "Bad length for OPEN (extended) %s (buffer underrun) %s" % (name, Capability.hex(data))
+                )
+            key = data[0]
+            value = data[3:boundary]
+            rest = data[boundary:]
+            return key, value, rest
+
         def _key_values(name, data):
             if len(data) < 2:
                 raise Notify(2, 0, "Bad length for OPEN %s (<2) %s" % (name, Capability.hex(data)))
@@ -216,12 +231,27 @@ def _key_values(name, data):
         capabilities = Capabilities()
 
         option_len = data[0]
+        # Extended optional parameters
+        ext_opt_params = False
+        # Non-Ext OP Len.
+        if option_len == 255:
+            # Non-Ext OP Type
+            if data[1] == 255:
+                ext_opt_params = True
+                # Extended Opt. Parm. Length
+                option_len = unpack('!H', data[2:4])[0]
+                data = data[4 : option_len + 4]
+        else:
+            data = data[1 : option_len + 1]
+
         if not option_len:
             return capabilities
 
-        data = data[1 : option_len + 1]
         while data:
-            key, value, data = _key_values('parameter', data)
+            if ext_opt_params:
+                key, value, data = _extended_type_length('parameter', data)
+            else:
+                key, value, data = _key_values('parameter', data)
             # Parameters must only be sent once.
             if key == Parameter.AUTHENTIFICATION_INFORMATION:
                 raise Notify(2, 5)